Telephone system



Oct. 19 1926.

' 1,603,267 4 H. B. BROWN TELEPHONE SYSTEM 10 Sheets- Sheet 1 Filed June13, 1924 Mi an/0r."

Oct. 19,1926. 4 1,603,267"

H. B. BROWN TELEPHONE SYSTEM Filed June 13, .1924 10 Sheets-Sheet 2 Oct.19, 1926. 1,603,267

H.B. BROWN i TELEPHONE SYSTEM Filed June 13. 9 10 SheetS-Sheefi 4 fie ry53 Brown.

Oct. 19, 1926;

H. B. BROWN TELEPHONE SYSTEM File d Jun 13, 1924 Oct- 19 1926. 1,603,267

' H. B. BROWN TELEPHONE SYSTEM Filed June 13, 1924 10 Sheets-Sheet 6Oct. 19,1926; 1,603,267

H. B BROWN TELEPHONE SYSTEM I Filed June 13, 1924 10 sheets-sheet '2 V yr Affy.

Oct- 19 1926. 1,603,267

- B; BROWN TELEPHONE. SYSTEM Filed June 13, 1924 10 Sheets-Shet' aWye/#0}.- Henry 5. Brown. i

3w a? 4 r v 6K e Qv v 9? n. in l.I-\l all. m Nmnmm Emm mu lnnlw P w R .2sfi Hi1 PM R Q \1 3st;

Oct. 19, 1926.

1,603,267 H. B. BROWN TELEPHONE SYSTEM.

Filed June 13. 1924 10 Sheets-Sheet 9 AffK/ "Oct. 19 1926 1,603,267 H.B. BROWN TELEPHONE SYSTEM .Filed June 13, 1924 l0 Sheets-Sheet 10 I/m/e/7/0/ flew/y E Brawn.

Patented a. '19,?1926.

- INCORPORATED, oFnEw YORK, .N. lY.,-=A' oonroim'r on or I NEW YORK.

Application i d June 13, se a it 719,750?

This inventionrelates' to telephone systems, and more particularly, to'a system wherein connections are established by means 1 of automaticswitching apparatus.

of ten keys nuinbered from 0 to 9.

in accordance with this invention each operator in a manual telephoneofiice s, provided with a group-of ten keysone 'forieach any distantoffice "T he digits thus of the digits 0 to '9, and a group of oificekeys one forv each office to which she has access. To reach anyjjflinein proper 'oflice key and then proceeds to write up in succession uponthe ten; keys,

the digits comprising the nun lo'erfl of 1 the, called line. writen upare recorded by a register sender. Depressing the ofiicekey',

causes one of a group of circuits','cal'ledlink the operator.

; digits comprising circuits, to simultaneouslyhunt for and seize thecalling operators po sition,'a'n idle: trunk to the desired'oflice, andfanidle register sender. V j" When an idle trunk s fo'und,the number ofthe seized trunk is visibly indicated. to 1 The registers in the sender:

are set succession in accordance with .the

.line, and fter the second digit has 'been recorded in the register"sender and an idle trunk circuit has beenfound, the first digit istransmitted over the trunk circuit in the form of mpulses and? one of atrain of switches at the distant mechanical. foifice is set. Whenthethi'rd digit has been recorded the second digit is transmittedgover,fthe

trunk circuit, and so on. WYhen the last digit is recorded,Ythe' plug ofa cord isiinserted T in the jackof the trunk circuit, and

the digit; last'recordediis then transmitted over the trunkcircuit."The' calledline', if

idle, is seized, and

spending" conversation' takes place -in "the. 'VVhen the last digit isis signaled, and uponreordinary' manner. 7

recorded, the position equipment is dis cherged, and when tli'e last1d'g1t 1s trans fmitted, the reg ster sender iSQalso disc'harged to,,,which she has'f'access' the operator .,-1nerely" depresses c the Fig. 2represents the number of the called j when the fc'over'sauon tmtie tadisconnect. signals {are given "to [the operator,

and disconnection takes place intheordinary way.

.A vfeature of invention airin s.

ment whereby the operator may at will'call any line, consisting of'anyn-urnberof digits, asdesiredp v Q I.

iernother feature of this, invention is the arrangement.wherebythedigits are recorded :and the proper selectionsini' accordancetherewith take place 'si1nultaneously one diginhowever, always beingheld in reserve have been recorded.

drawings comprising ten sheets nu nhered Figsfl to 11 which areplacdasindicated, r .in Fig. 11, the invention is schematically set- I,

forth.

until the operatorindicates thatall digits;

Fig. 1 .represents a callingsubscribers -h'nej1nfa manual; oflice andaatypicalcord Qther features-will appear [from thjde tailed description]whichyfoll ows' z In" the 1 5 circuit commonly'used in establishing aconand any. called-line.

nection between thecallin' 'lline' as indicated allottin g an idle linkcircuit such as is disclosed inIFigs-A and 5;

shown, which' isused in 'routinga connec- 'tion'to a trunkifinderswitch"such asthe'one shown in the center; of Fig. 8, or at the right oiIFigLZQ J' m, Fig. i 5 :2; 'pe'siedn gfincii i switch ands senderjselectoi'fswitohi are'a'lso shown. The Q 7 trunk: finder switch ,i(lig. '3jor 45), position 9 .iinderlswitch (Figs) and sender selectorswitch (Fig. 5);.areallQcontrolled 'by' the the 'allottercircuit At .theleft, Grie a steering sweet is linkcircuit (Figs; 4128161 15,) sothatas-soon as a call is initiated, the link circuit functionscausingqthe jtrunk "finder-switch, position finder switch andSenderselector switch tdr'opsatesimultaneously to findfrespec: 1-1

Fig. 7 'the fposition. indicatingf'equipin'ent, which fis iisedit'oindicate to the op;-

erator' the number lot the trunk? seized-f Zby tively, the first idletruiik, oalliiig posi the trunk finder -I't "she mi-t understood i the?es 91 s efli e ey simi ar-M1 key;

610, for each distant mechanical ofiice to which the operator hasaccess.

In the upper right-hand corner of Fig. 3f

and in 'Fig. "'8 are shown two trunk circuits, such as" are used inestablishing a connection to the distant mechanical oflice (F1g4 8);

Fi'gs.-i9- and IO-show the register senderequipmenhficonsisting "etagroup of registers which are set in Various combinations under controlof the numerical keys (Figl fii to operate the counting relays (Figloiwhich count off the number ofimpulsestransmitted over thetrunkcircuit to the distant mechanical 'ofiice for setting the automaticswitches therea t. Aninterrupter "shown at theupper right hand corner ofFig; 9 is used for producing the impulses. required. The sender alsoprovided, as indicated at T.

'S. with a "timing switch fo'rlmeasurin'g off a definitetime intervalbetween each trainrof impulses transmitted to the distant 'oiiice', topermit "the switch at the distantoiiice to-have sutlicient time to trunkhunt before another series of impulses is transmittec ly'a "recordingswitch which advances one step "for each digit recorded by the operatorto transfer the register leads from one group of registers to 'the nextsucceeding group; and a sending switch which is operated by t heinterrupter to control the 'transmi'ssiono'fimpulses to' thetdistant me-Answering call.

WVhen the receiver is removed from the switch-hook at the substation #1,(Fig. 1) the line relay- 2 operates over an obvious circuit includingthe substation loop, and the line ilanrp=3 isulighlted. The plug of thecord-6 is inserted in the jacl' 5 opera'tingthe cut-oil relay 4, therebyopening the circuit through the line relay 2 which releases eX-assume'to be. the substation tinguishing the line ilainp '3. Thesupervlisory' relay 18 is operated thereby preventing supervisorylamp 17from lighting. Listeninglrey 8 is operated, connecting the operatorsatelephone set to the calling substation l. The 'cailfling substation-J1givesthe number of the 'clesiretl :line which we 'wil l a distant-central office :of a full mechanitcal-step-by-step system.

N p 7 I Operatifl'lz'nlc circuit. V I The key 610 i 6'), which isdesignated by a code corresponding to the centraloflice icsja easans er?to ground, The

depressed by't-he operator, closing .a' circu t to operate relays 613and-619 as 'follows: battery, armature 633 of relay 618,j63 t,urightlwinding of relay 619, 635, left-winding of relay 613, 636, 637co-ground. Relays619 and 613 operatedv lock by way 'oi' H V 7 7operation of the ofiice key 610, also closes an obvious circuit tooperate relay 612. When the otiice key 610 is released, relay 611operates in series with the winding of relay'612 and relays 61-1 and"612 =lock'in s eriesto ground at armature 669 of relay 619. j

There is a group of link circuits for each trunk "route to 'which the'eperaitor :has access, and an idle-link circui t is always preselectedby the selector switch of the allotter circuitso that thebrushes 230 to235 inclusive oftlie selector switch in Fig. 2 are nor- :mally restinguponthe terminals. of an idle link circuit, whichwe will assume tobe thelink circuit shown in;Figs. 5. Under these circumstances theoperati'onpt relay 613 will'close acircuit to'opera'te relay2D0 (Fig. 2)as follows: battery, armature 638 I of 'rela'yfile, 639, 625,"501,-2%,"resistance 201 in parallel with the winding ofre lay' 200resistance 202 in series, "to ground. Relay 200 operated operates "relay205 'as follows: battery, 206, 207,208, winding or relay 205, 209, 210toground. Relay 205 operated locks by way 'o f' its armature 239 to groundand (i'pe'rates relay 24-6 over an'oh VlOUS CIICHlt,

associated with the bridge '236 fthereby' 'preventing relay 288 fromoperating thus rendering brid'ge236 ineffective, until "the first ela24r6opera'tedopens 210 the ground to the winding of relay 238V bridge250 I we performed its function, after relay 246're1eases,

'iVhenf the interrupter 251 is closed relay 247 operates overthe'following circuit r battery, armatureaee of rela 2 11, winding-cfinterrupter. 251 247 operated connects relay 247,249, 259, ground.tRelay ground byway creams the winding of re 251 is opened, relay alarmsignal unless relay {211 hasoperated in the meantime .as;hereii1aft2rdescribed.

' Relay'508 operated lo clrslby way oitih,

5 86 and 589 to ground,v-and closes acirc'uit to operate relay 509 asfollows:Qbattery,

511,512, 513 to L to operate relay 11-7 as winding of Irelay 5019, 510,ground; and a circuit follows: battery, left winding =of relay 1 1?,

5116, 5915, 510., 511. 512, 513, to ground; The function ofirelay 117will be hereinafteiideoperatecl-locks;as follows: battery, winding ofrelay 509, 59.61

scribed. Relay 5 09 52 4 0; a p a-t e 513 to'ground. Relay509'foperateii con way of 203, 500,

- overthe following circuit: batter-y,

C: Cl

to'that shown in Fig;

i i ,7 to operate nect s battery to the networkconsisting ofresistances201 and202 and 'the winding of relay 200 asfollowszbattery,armature 519 of relay 588, 518, 517, "516, 515, 514, ,500, V

' this manner, an idle link circuit if available is always preselectedby the allotter circuit,

203, 202 to ground.

it Will be recalled that a circuit was closed when relay 6l3;operate'dbyway of. 625- and 20410 operate relay 200. When relay 509 operates aspreviously. described,

thecircuit including the resistance 202v by etc, balances the circuitincluding the resistance 201 by Way of 1, 501, 625, etcJa'ndthus thepotential at 255 1 and 256- is substantially the same; hence re-vlay'200 releases, opening at 206 the circuit through-relay 205 whichalso releases.

operate relayv 523, asfollows; battery winding'ofre1ay523, 524, 525,526, 527, 4100,

;.401,402,403. -101,-52s,529,.,512, 513 to ground. Relay 523 operatedlocks by; way of "537,"512 and 513 to ground.

The stepping magnet 227 now operates windingof theqstepping magnet 227,226, 217,

218, 219, 228, 229. brush 230, 210,520, 521,

' :522 to ground: :Relay 2l1. operates in paral lel withsthe steppingmagnet227, and opens u= at 248- the circuit through relays 247 and 258which release.-

. takeplace; ing properly before interrupter251 is again 'Theseoperations all only incase the call is progressclosed so'thatr'elay'252willnot ordinarily h'ave a'chance to operate and by i0pBIat1ng relay 261start the trouble .;alarm 253.

V .Presleoting a nfic lle The stepping magnet 227 operated, opens at 226its own operating circuit, thus releasing and stepping the brushes 230to ,235

, inclusive'one step in an anti-clockwise dilink circuit similar towhich the brushes 230; to 235" inclusive are "now connected is busy,*therelay; corresponding, to relay" 523 rection. If the nextwill be operated'and'ground will be conits lead corresponding to lead 240 to:th'e'brush" 230 "andxthe' circuit the stepping magnetf227 will agairi beclosed causing itto' operate and; V again release {and rotate the 235inclusive nected 'by way ofanother step. This cycleaof operationscontinues until the next idlelink circuit is' such Jlink circuitcorresponding to. jrelay' 523 found; in which case 1 the relay in will not be operated, hence groundiwillnot itslead. corresponding to be";connected to 11 M210,- and the circuit to operate the; step "ping;magnet 227 "being open; the magnet will.riotf re'operate, "and relay 211will, re- "lease. As long jasthe stepping magnet 227 is" operating andreleasing,

freinoving 1 ground 55212 from: brushes; or 231f2LS'tl1Q case maybe-prevents the re;

. Relay 509 operated also closes a circuit to of relay to be very 589 toground.

releasing,

,Iclockwise direction.

positon finder. jswitch1 brushes 230 to to relays 508' or 598 fromperating until an idlel ink circuit allotter circuit Fig. 2 isagain/normal. In

408 "as follows: battery, winding of relay408, 476, 521, 522, to ground,The function of relay 4:08Whichis designed 7 slow to operate,ishereinafte'r more fully described. Relay 53.8 operated closes'a hasbeen found and the,

v to groundfltelayalsocloses a circ'uitto start the operation laysi'n-the preselected' li'nk corresponding 'right-windingofrelay.538,54c7,'548, 519, a559, .brush 540, 59.6, .513

circuitfto' operate. relay, 539 as \follow's':

battery, left winding of relay 5 39, 569', 579,

ltelay 539 operated locks as follows: battery, right winding of relay539, 5010, 521,522 to groundI,,A lcirc'uit is now closedtooperate'thestepping mag. net 536 of the position findergflswltch. as "follows:battery, windingof the stepping magnet 536. 558, 568,578, 569,- 579,"589 to ground.

The stepping. magnet 536 operated opens at 5155'its own operatingcircuit thereby: 7

5 15 inclusive to rotateron'estep in an anti- The function offlthe pingmagnet 536 is attempting to Relay 613 of every. operators position andcausing the brushes 540 to i K with which the stepe 1 associated isito"theparticular'position whose operator is establish. a. connection withthe step-by-step central oflice shown 1111 except the position we areseeking will be normal hence, groundzwill be connected to every terminalin the are 530 except the terminalto which lead 502 is, connectedwhicl'i 1 willibe econnected by way off626, .657, left winding of: relay614:, and 633' to battery, I

The relay 538, will remainlocked. over bridgsing brush 5 10 togroun-clontheyariousten -min'a ls'i the arc ntilbrush5l10 comes to restupon the terminal to which lead 5021s connected when relay 538 releases,open-; 'ingiat 579thecircuithofthe stepper mag i net 536. whose brushes540m .545 inclusiye now remain .atfrest upon the terminals as 1 sociatedwith the:.operatorsl,position sliown. i

in Fig.6-

I Relay 538"released closes a icir.-- @1111; to operate relays A105 andv614- .as fol 1 lows battery, armature 633 of relay 618, left,windin'gofrelay 61 4, 657, 649,626,502, 5410,

5'56," 406 winding operate relay 538 as follows: battery, flet'tz i Cit.tors position to test busy to all other-positionfinder switcheswhichmay be hunting at this time or at any time while this call isprogressing.

' Relay 405 operated closes a'circuit to operate relay 58.8 as follows:battery, winding of relay 558, 599, 409, 418, 419, 402, 403,- 404,

528, 529, "512, to ground. ,Relay 614 operated locks through its rightwinding byway of 648 and 647 to ground and opens at .638 the batterysupplied by way'ot 625 and 204 to t'heresistance 201 of the bridgenetwork'(Fig '2). The operation of relay 614 opens at 648 the holdingcircuit through the left winding of relay 613 but the latter relayremains looked over. the following circuit: battery armature 63.3 ofrelay 618, 634, left winding of relay 619, right winding of relay 613,e57, 649, 626, 502, 540, 559, 540, 548, 547, 55 7, 556, 406, winding ofrelay 405, 407, 567, 577., 587 to ground. Relay 588 operated, opens at519 the batterysupplied by way of 500 and 203, to the resistance 202 o'fthe bridge network (Fig. 2), and closes the following circuit to operaterelay 575: battery, '519, winding of relay 575, 525, 526, 52 7, 400,401,402, s, 404, 528, 529, 512, 513, toground. The function of relay 575will be described in detail under selecting an idle sender. Battery isremoved-from leads 625 and 204 under control of relay 614 slightly inadvance of the removal of 'batteryfrom leads 500 and 203' by theoperation ofrelay 588.]. This precaution is taken to prevent theunbalancing of the bridge .in'etwork from momentarily reoperating re-*1a 20.0. I It Should bejobserved that only the posi- .tion finderswitch associated with the step ping magnet 536 is used at this time.There are five postion finder switches of .which three are omitted fromthe drawing (Fig. 5) only the first and last switches being shown.

I Since each switch has a capacity of twenty 7 group of 20 operatorswill only function =5). when an operator in that group is seeking 1operatorsthe total capacity of all. five switches'is operatorsythe lastposition finder switch. being associated with the last to establish acall "tothe otlice shown in 8 In case the operator initiating the callis in the .last group, the lead corresponding to v625 associated withthe last bridge network (it should be observed-that there is atotal of 5leads similar to' the lead 625, one tor each. group 01620 operatorslwill unbalance thelas't bridge'netwoik 236 in which case relay 237' willoperate in turn operating relay'238. Relay 238 operated will close acircuit tooperate relay 598 as follows: "battery, winding of relay 598,241, 231, 254,260,213,

212, to ground. Relay*598 operated, will. function in general in the.same Inanneras relay tog-whose functions have already been nest.5.44,4114.15444455 44; A circu t jsertsthe plug 10 ofthe-cord-circuit(:Fig.

in the trunk jack 807- ("filsas finder switch associated with thestepping magnet 536.

Tmmk sition finder switch was huntingfor thezpartic-niar callingposition, the sender selector and trunk finder-switches wererespectively himting for an idle sender and an idle outtrunk in themamier hereinatter ide .It should be observed that whi:le.:the:po-

outgoing trunk similar to necting ground by wa of 808, and-43.1.t0

the associated terminal of the are. 411, .or; the relay corresponding torelay 438 will beeperated to connect" ground to the brush correspondingto brush .421. In either. case if brush is resting uponthe ltenniinal.eta busy trunk there will be ground 10.11 the corresponding terminal ofthe M0411. An (JP- crating circuit for the stepping magnet426 is nowclosed as tollowszbattery, winding of stepping magnet 426, 427, .428,328, 307,

420, 434, 435, 436,322,- are, 346,317.,

437 421 to ground on.thehuntinmterminal i ("J b of the trunk uponwhichthe :brush 4216s new resting. The ground on .this lulntir gvterminal short-circuits. irelay 3438] whose winding is also connectedtog-ground at contact 439 of 'relay'417 thus preventing relay 438 tromoperating atthis. time. ",Thestepping magnet 426 in operating opens at.427 3 its own'o'perating circuit and releases, thus steppingitsfbrushes410 to 4-15 inclusive {onestep to the terminals of the. next trunkin thegroup. This cyclewo f operations conti nues until an idle trunk. isfound at; which time the hunting lead corresponding to lead 431. will befree from ground. W/Vhen an idle trunk, which we will assume to be theone shownin. Fig. 81's toun(l,ithe groundwvhich previouslyshort-circuited relay 4438 ;is removed permitting this-relay totoperatevin series with. the stepping magnet 426, but the steppingmagnet 426 will not reoperatefldue to the'high resistancerof thewinding-of .re.-

lay 438 in series with it. ltelay-438operated' conn cts ground .at 435byyway otg436, 322,

312, 316,317, 437, 421, to 431,'c1a.using=the t'runk selected to testbusy. to all other. trunk finders in the group. .It 5 is necessary j toi connect this g'roundto the. lead 431 to cause the trunk to test busybecause the busy ;.ground on the lead 809 under control of relay ,806will not be supplied until'th'e operator iner lainpsbeing lightedtoindicate the trunk from 0 to 159. Each first group and ground.

to ground. 1

- atz'ag the trunk Y After the trunk and the positionhaveibeen found it.is necessaryto designate tothe jop': erator the number of fthejtrunkfselected. This is accomplished by meansof' agroupoi number. 7 I, I1

It has been determined that160'j trunks between oiiices is a reasonablenumber to allow under the worst traflic cond tions be -tiveen busy0tfices,hence this circuit is ar-" ranged to indicate the number of anytrunk trunk finderswit'ch 1s exceeding '20 trunks,

traffic conditions. eight trunk selector switches would be required inorder'to. obtain a maximum of 160 trunks. For the purpose ofillustrationonly two trunk finders having a maximum of trunks havebeen shown, butthe explanation which follows applies to any number of groupscomprisingfrorn'l to 160 trunks as required, the only difference beinginthe amount ofequiprnent used.

'Assuming that the trunk picked is in the is trunk No. 10 asjshown' bythe position of the trunk leads in Fig. 4

' of the drawing, it will be necessary to indicate' to the operator thattrunk No. "10 has been selected. to 315 of the steering switch w1ll beresting .upoi 1 the fourthterminal of their respective arcs, in whichposition the, first trunk finder switch is used. 'lheoperation of*relayJ474 connects leads 7 22 and 721 of the trunk number indicator(Fig. 7) by way'of leads 622 and'621, 545 01 the position finder switch,leads 590 4114591, 490 and491, 492 and 493, 494 and 495, 324 and 325to'brushes 314 and'315 of the steering switch. In this casebrush314resting. on. the fourth terminal of the steerencounters an open. clrcuitc'onmg switch dition andlead622 remains open. Acircuit is closed,however, over lead 621 as follows: ground throughthe left winding (highresistance.) of relay 480, brush 315, 325, 495,

4.010, 491, '591, brush 545, 507, 21, 721,

'. 7 32, right winding of relay 709, right wind 725, 720, 620, 630,-631, w

ing of. relay 713, I battery. Relays480 (Fig. 4) 709 .(F1g'. 7) operatebut relay 713 being marginal does not operate due to the highresistanceof the winding of relay-480 in series with it.

,Ptelay 709. operated, looks through. its left winding by way of 745,724, 624, and'647 to Nith relay 709 operated, acircuit is closed tooperate relay 704 whichis designed to be slow to operate and whichoperrelay' 7 Relay 703 In this-case the brushes 310 I ates relay leads506 and 507, brushes 544 and ates and, closes an obviouscircuit tooperate is'likewise designed to I -Belay"703,- operated, transfers theleads 722 and 721 to the wind be slow. to operate."

ings of relays 710 and7'14, and of 7 11 'respec-' tively.1fRelays 703.andl704are niade slow tooperate sothatwhen relay '709 -operates721'a11d722, the t'ransferjofthe register closinglthe operating circuitsforrelays703 and 704 in succession -to 'transfer the" leads relays; willbedelayeduntil after relays 480 and 481 in the link circuit (Fig. 4) arelay 482 'whi'chwilloperat later to transfer the leads'492 and 493' 4) tothe next .iiully operated" preparing the "circuit for re succeedingresistance network of the register control combination." Bytransferringthe register leads 721 and 722 firstfno dif v p p .ficultyis experiencedbecause each transfer arranged to hunt over a'trunk group of not henceunder the worst;

in the; register circuit (Fig. 7 changes the circuit'condition frombattery to ground or. from ground to .batteryfas the case maybe,

or ground jto a ground circuit as the'case may he, the'succeeding groupof register relays {(Fig. 7 isnot Tafiected. It is'only' when thetransfer is completed in the link circuit 4) that thefnextsucceedinggroup 'of register relaysare capable of being operated. Theoperation 0r-re1 y4s0 in ithelink circuit closes an obvious circuit tooperate relay 481'. which locks undercontrol of relay474. Vfhen' relay703 finallypper- 480 releases, closing'a circuit to ne'registercircuit.before completing operate relay. 482 thus transferring leads 1492, and93 in the linkcircuit (Fig.4) to brushes424. and 425' of the ,trunk'[inder switch, .Briishes 424and425 have taken the same setting as thebru'shes 410 to 418 inelusive, which in "this case will be the eleventhcorresponds totrunk'10! terminal {or their.v respective are which 7 The.eleventh terminalof arc" 4141 4154 connected to the resistanceIlJGtWOIlQflIBIlCE ilead remains open, preventing; either relay 710orrelay 714 from operating. But a circuit is closed over'1ead621 tooperate relays711 and 483 as follows: ground, winding of relay 711, 732,721, 621, 507,; brush 545, 591, 491,

p v right-windingof relay 483 (high resistance), 484,485, 486, 487 .580,581 to battery. Relay 711 operates and locks "and closes an obviouscircuit to operate slow operate relay 707, which N in' turn operatesslow operate relay 706. Relay 706 operated,

operates the slow, operate relay 705, thus 7 498,441, brush 425,eleventh i terminalof' arc vv415,

transferring leads 721, and722to the-leads 726 and 727' leading to the,relays 715, 716,

' 7 "to ground,

the 713i 13313 706, 3114707. are

designed 'to be slowto operate to permit relay 483 to operate beforeleads 721v and 722 are again transferred;

oiiereftiiig 3116331313 3. 11313 713 and 717 15 3434 switch'the mainbatteryfeed forliglitihgjt 1e tens lamps from the even to the odd lamps.The, zero hundreds l31hp700 willnew he lighted from battery at 765,15111112700, 734 to ground. The tens lainp"(728 will now be light-edfrom battie by, at 7111314113 728, 743, 744, 734 to ground. Tl 1eu'iiits13111 729 will. now be lighted trofri'battei'y a t 778, 13111 729,750,751, 734, Hence the lamps displayed will read 010 indicatingtIlllllI number 10.

Assuiniiig that at the time of trunk ellth e triinks'connected to thearcof trunk finder switch (Fig.- 4) are busy, thenthe stepping niag'iiet426 will continue to operate 3nd rotete the brushes 420 to 425 inclusivestep-by-step until they sire resting upon the terininsl twenty-first 111each of the 31 3 419 13 iiiolusive. At this time brush 421 will beresting uiion the teriiiiiizil 449 of the are 411 Mid as this terminalwill 7 be connected toground the circuit to opertte the stepping magnet426 (previously traced): Willbe. againv closed aiid the stepping m aghet426 will reopera'te. The stepping magnet 426 will be prevented from re-7 leasing; by the, closure ofthe following hold- III.

in}; circuit: battery, winding otthe steppj g' magnet 426, 443', 329,311,. 321, 447,424,

446, 4:45 ground. A circuit is now closed operate the st pping i iag'net306 of the steei ing switch F ig. as follows: battery, wihdihg ofthestepping hiagnet 306, 308, 3,20,. 3 10, 327, 444, 443, 477, brush 425,497, 440 to ground. Thestepping magnet 306 opens at 30 8 its ownoperating circuit and r'el eeises, thereby rotating the brushes 310 to315 inclusive onestep in an anti-clockwise direction. When the brush 311advances, the holding circuit for thesteppi'ng magnet 426 is opened,releasing the stepping mag- 114342'3 and rotatihgthe brushes 410 to 415inclusiveof thetrunk finder switch one step in. an aiithclocliwisedirection. In this po- 4) ,will be repeated.

siti'on' all" the b15111she's1 except brush 1 32 out i of Contact withany terminals" of their respective arcs; The are 411 has one ter niinal'more than the other arcs of the switch. Consequently, in this position,the brush 421 is resting upon the terminal 440 and is, thereforeconnected to gr'oundet that point. The brushes 410'to 415 incl t sive'will remain in this position and the trunk finder switch (F ig. 4) willnot again beuseduntil all of thetrun'ks in all 01 the other' groups tothe same distent 01-11 4 have beenhunted over, h V

1 The trunk fiiider switch associatedwith the stepping magnet 306 (Fig.has access to otl1ei-"groups' of trunks to the same other trunli tinderswitch such as the one shown in F ig. 3 from its normal position andcause it'to seek an idle trunk in the fie tt group of trunks to which ithas access; the normal position of the trunk fi der switch 311 thebrushesexceit'the brush341 are out of engagement witl i' any of thefter}minals of their respectite er'cs'. The- 3111311 341,, however, Will berestihg upon the" t er inin all326 and as sooiies the stepping'nisg net306 has advan cec'l iii, the; masher pfeviously d escrib eol tcireu'it'will'be clbsedto operate the steppiiig ine'gi'iet' 336' followsbattery, winding of the stepping ihegnet 33 ,337,333, 313, 323, 429,434; 435-, 433, 322, 312, 35 1, 341, 323 :3 ground. Stepping magnet 336opens zit 337 its own'operetiug circuit and releases, thus rotating thebrushes 340 to 345 inclusive one step an anti-clockwise direction to theterminals associated with the first trunk in the roup. The tr'uhlisunder control-' of the ttunk findei switch ig. 3) are now tested in thei same generil' manner as were those trunks accessible to thetrunlttinde'r switch (Fig. 4) arid the eyc'le'of operations (previouslydescribed) ofthe trunk finder switch (Fig. If all the trunks of this grop 3. 76 busy the brushes 340' to 345 inclusive will rotate step b'ystep'until the last trunk in the group is passed and the twenty-firsttern'iinzil in each arc is reached. In this position the stepping magnetwill be prevented from releasing by the 'closure of the followingholding circuit: bate tery, winding of the stepping magnet 339, 311,321, terminal 346 iii thearc 334,

brush 344, 347, 473, 446, 445 to ground' A circuit is new closedtooperate the step;- ping nieghet 306 as follows: balm- 7,13 134- iiig,ojtthe steppiug magnet 306, 308 320, 310, 318,319, terminal 348 intheare brush 345,. 349, 479, 497', 440 to ground. The stepping magnet 306opens at 308 its own; operating circuit and releases, rotating itsbrushes 310 to 315 inclusive in ah anticlockwise direction and thusbringing into piay another trunk finder switch not shown with.

V the ot trunks associated -there- This trunk, ail-(161 switchinot shownand the stepping magnet 306 will function in thelgeneralmannerpreviously described for I the-trunk finder switches (Figs. 4 and3) and the steppingmagnet" 306 will operate and rotate'the brushes 310to315 inclusive another step to the leads associated with i anothertrunk finder switch. This "cycle of operatlonscontinues until one of thetrunk finderswitches locates an idle trunk to the distant officej shownin Fig. 8."

It should be observed-that when all the trunks to the dist-antofiicehave been hunt ed over the trunk finder switch 4) will again come intoplay and the 'steppingmagnet 426 will advance the brushes 410 to 415inclusive of the associated" switch to theterrepeated;

ininals as'sociated 'with the firsttrunk in its group and the "From'theforegoing description it is'evident that'when any trunk finder switchad- ;vancestothe twenty-first po sition,"a c 1r- 'cuit is prepared foroperating the stepping 'inagnet of the trunk finder switch. by way ofeither lead 329,01 339 etc., and the twenty-first terminal of either"are 414 (Fig. 4) or 334 '(Fig. 3); In this position of the trunkfinderswitch a circuit is also prepared to operate-the stepping magnet306 of the steering switch by way of either I ,7 lead 327 and thetwenty-first terminal of are 415 (Fig; 4) or by way o'f'lead 318 and theI twenty-first terininalot are 335' (Fig; 3), 7

' It is necessary tot-make sure that the stepping magnet of th'e trunkfinder switch is fully operated before the brushes of the V steeringswitch advance, that is, it-is' neces- V sary to insure the properoperation of the contacts is closed. As the contacts in question areadjustedv so that they donot close until thestepping magnet of thetrunkfinder switch is fully operated, itrfollowsthat the steering switchvwill never be able to operate-in advance of theistepping magnet of thetrunk finder switch. 7 p In order to insure the proper advance ofthesteering switohthe holding circuit for the stepping magnet of thetrunk finder switch is controlled by wayof brush .311 of the steeringswitch. 'J Accordingly the holding circuit 'forI'the stepping magnetof-the trunk finder switch is not opened until the steeringswitch'hasactually advanced. f So opened by the cycle of operations willbe u the holding circuit for its stepping magnet switch,

' Selecting an idle s ender.

Vvhen relay 417 was operatedin thematilong asthe stepping magnet of thetrunk. finder switch is operated the 'assooiated. "brushes cannotadvance, hencefth'e" trunk I I finder switch cannot return tonormaluntil advance of the steering her previously.described afoircuitwas closed to operate relay" 455 as follows} battery,

right winding of relay 455, "457', 456 sto variousterminals in the; arcs550 to 555 inclusive are connected to similarlyvvsituatedi term nals ofthe corresponding arcs of other. sender selector switches. W hen thesender is "busy-ground will beconnected to 'it's hunting terminal in theterminal are 555 in the following manner: any terminallin ground; Itshould be understood that the the are 555, common strapping,corresponding terminal in the are (sim-' .ilar to are 555) of the switchwhich brush is retaining the sender busy, corresponding to 565, leadscorresponding to 592, 451, 452, 450, winding of relay corf responding to460,461,462to ground. Due

to the low' resistance of the winding of re-, lay "460, the busycondition described will 565 is resting upon the hunting terminalassociated with a busy sender, relay-455 (Fig. 4) -when operated in themanner previously described will lock over the following circuit:"battery, left"winding of relay 455, 452, 451,. 592, :brush 565, huntingterminal of the'busy sender to ground Re lay 455 operated closes anobvious circuit through the right winding of relay 454 causing thelatter relay to operate and lock through its left winding by way of 457and selector switch as follows: battery, stepping magnet 594, 593, 459,458, .457, 456 to ground. The stepping magnet .594l'in operating opensits. operating "circuit at its own interrupter contact and. releases,rotating: the brushes not be affected. (Assuming thatthebrush 1 456 toground, A circuit is now closed to. operate the stepping magnet594 ofthesender J ranged to bridge adjacent terminals ofthe are 555 .whenthebrush is rotating, butv to makecontact with one terminal" only when thebrush is centered. .Hence as :long,

as the brush 565 encounters a grounded ter-- ininal thefholding circuitfor relay 455gwill' I I remain cljosed, and the stepping magnet 594 Iwill continue to operate-zand release, rotating the brushes 560 to 565'inclusive stepby-step until thebrush 565 is centered upon aterminal inthe arc 555'associated with an idle sender. 'In this position the.holding circuit for relay 455 willbe 'openedreleasrelay 455, and openingat 458. the oper- 560 to 565 inclusive one step in an anti clockwisedirection. The brush565is ar relay 463 and'the relay 91 closes anobvious circuit to operate relay 913'. Relay 463 operated connectsground by way of 465 and464 tothe winding ofrelay466, but the latter.relay will not operate at this time as'it is short circuited by theground supplied at 467 by relay 460.. Relay 913 operated connectsbattery by way of 914,

and1090 to the. windings of the various register relays of the registercircuit (Fig. for a purpose hereinafter more fully described.

Theoperation of relay 463 completes a circuit to operate relay 574 asfollows: battery, winding of relay 574., 573-, 572, 468,

469, 456 to ground; Relay 5'74 operated extends the 'registrationdeads627, 628 and 629 (Fig: 6") to the leads: 926,927-

, spectively of Fig. 9. It is desirable to keep these two sets of leadsseparated until" the calling operator s position and an idle sender Iare linked togetherand accordingly relay 574 which,when=operated effectsthis pur pose", is prevented from operating until the callingioperatorsposition and a'n idle sender 'haveboth been found by the link circuit.

' The operation of relay 463 also completes a": circuit for'theoperation of relay470 by of 471 473V and 472 to ground. Relay 4520operatedextends leads .432 and 433 of the 'outgeing-trunk circuit (Fig;8) to the leads 920 and 921 respectively of the sender (Fig. .9) toclose'in apart the fundamental circuit for a purpose hereinafter morefully described; It is desirable to prevent leads 432' and fro1n= beingconnected to the leads 920Iand 921 until after an idle trunk circuittandan idle sender have been found and the special function of relay 470isto keep these two sets of leads separated until th'elink cir'cuit'hasfound both anidle trunk and-an idle sender.

Relay463 also provides a holding circuit I for relay 417 as follows:battery, right winding of relay 417, 496, 469, 456, to ground: and alocking circuit for relay 588 as folloiwss. battery, windings of relays588 and 5 85,.5011, 584, 489, 496, 469, 456, toground. Relay-.585 doesnot operate at this time, as it is' short-circuited by the operatingcircuit of relay 588 previously traced to ground at. 513. of relay 508.

1 Sender waiting.

' Having found the sender a circuit is closed from battery, contact 914of relay 913 in the sender (Fig. 9), lead 1000 left windings 0r relays10.121 and 10,11. in series, .1014, 947, brush 964, lead 927, brush.563, 5012, brush 54.1, 503,627, winding ofrelay 616, 640,.

641, 669 to ground operatingrel-ay 616 which loclrsby way of642, 630,631, to batteryand e inguishesthe No sender lainp 632 ,as'

an indication to the operator that a sender is now attached and thatshemay proceed to register thenumerical digits of the called number.Relays:1011 and1912-donot operin to the thousands digit in which case. a

circuit will be closed as follows to] operate relays 1011 and 1012:solid ground atthe armature 64? ofrel ay 619 654, right1make contacts ofkey'Nor8', lead'627,=503, brush 501.2, brush563, 9 27, brush 964, 947,1014, left winding of relay 1011, left winding of relay 1012, 1000,;914to battery. Relay 1011 which is. sensitive operates whenever by anumerical key closure, av ground condition is connected tolead 927 butrelay 1012 which is marginal only operates when sol-id groundisconnectedto lead 927 by the closure of a numerical key. I operated looksoverlead 10.00 to battery. A circuit is also closed tooperate relaysand. 1010 as follows: ground on the armature 647 of relay 619, 654,674,left contact of key 608, 646, 645,-lead 628, 504, brush 542, 5013,5003,. brush564, 928, winding of relay 922, 948, brush 963, 949, 1015,

right winding of relay. 1010, 1000, 914, to battery. Bela 1010 looksthrough its windingsin series. elay 1010 operates only'when solid'groundis connected to lead 928.; relay 92-2 is sensitive and operates whenevera ground-.condition'is connectedto lead 928 ire respective of theresistance of the ground condition. I,

It should be observed that whenever a ground condition is appliedtothelead 926, relay 916isoperated.

Whenever the digit sent is higher than 5, it is necessary to operateone' of the relays 1013, 1023, 1033 or 1043, as the case may be, inorder to add five counting relays to the circuit so as totransmittheproper number of impulses to the distant mechanical ollice(Fig.8);

Since the thousands digit is 8, it'is'necessary to operate relay 1013..This is accomplished in the following manner: from battery on the makecontact 9140f rela Relay 1011 Y y 913, over the common batterylead 1000,

locks under control of relay I 'eration of relay 922 also closes-at 966an winding of may 1013, first tarnish of obvious circuit by way of lead967 to operate the stepping magnet 956. So long as the "969, 977, 9 7.and 966 in parallel with the tact by "way of 9 key 608 is depressed,relay 922 remains op- "erated and the stepping-magnet 956 cannot releasebut as soon as key 608 is relay 922 releases. Y

Relay 917 also operated byway of 968,

released,

stepping magnet 956 to ground under con-,

trol of relay 922. Relay 917 operated locks by. way of 968,969, 977,967, 978 to ground and connects ground through its make 0011- 78 and 967to the winding of stepping magnet 956 to insure the step ping magnetsproper operation though relay 922 only operated -momentarilv when thekey 608 wasfdepressed. Re-

lay '91? cannot release. until the stepping magneti956 opensitsjinterrupter contact 977 at the end of its operating stroke thusinsuring the proper operation of the stepping magnet 956 no matter how'short a spaceot-time the numerical key 608 is depressed by the operator.When the step ping magnet 956 opens its interrupter 0011- 1 tact 977 theloclring-circuit forrelay 917 is opened and this relay releases openingthe holding; circuit for the stepping magnet 956. which likewisereleases advancing its brushes 960 to 965, inclusive, one step in ananti-clockwise 'direction substituting at brush 963. relay 1020 forrelay 1010; at brush 964 relays 1021 and 1022 for relays 1011a-nd 1012and at brush 965 relay 1023 for relay "When key 608 is released, groundbyway of lead 927, brush 964 and leads 947 and 1014 is removed from theleft winding of relay 1011. and relay 1012 now looks v:trom battery onlead 1000, left winding of relay 1012,. left winding of relay 1011, 1014and right winding ofrelay 1012 to ground.

Ni e are now ready to send the'hundreds digit which in this case isdigit 1 and accordingly, numerical key 601 corresponding to the digit1'is depressed, A circuit is now closed to "Operate relays 91.6 and 1020as follows: ground at armature 647 of relay second terminal of are 953,1090, right wind ing of relay 1020,1000, 914 to battery, Be

lay 1020 locks through its windings in series. Relay 91.6'operatedcloses a circuit to operate relay 917 as tollowsi battery, windingotrelay 917. 968. 969,977. 967, am ground. It alsocloses a circuit tooperate winding of stepping magnet 956, 967, 959

Even I erating stroke," when 917- releases. 'This circuitarrangementinsure's the proper op- I eratlon of stepping magnet956-1ncase the relay 9 16 isonly operated moment'arily by e themomentary depression of 'key 601.

When key 601 is depressed, a circuit is also closed to operate 1021 as,followsz I ground at armature 647 of relay 619, 654,

resistance 650 right contact of key 601, 680,

627, 503, brush 541, '5012, -brush 563, 927,

brush 964, second terminal; of are 954, 1eft windings of relays 1021 and1022 inserie's,

1000, 914 to battery Relay1022 is margileases. pWith "relays 9'16 and9:17 released, the holding circuit for thestepping magnal and'will notoperate chietofthe high 're- I ;sistance of the resistance "650.111series' 'with it butlrelay 1021 which is sensitive operates net 956 isopened andthe stepping magnet releases advancing the brushes 960 to9.65,

, inclusive, another step in'an anticlockwise direction were thirdterminal 0f 'e' aoh of the-arcs 950 130 955 inclusive? '1 the thousandsThe operatorhaving I p and hundreds registration, the sender will nowproceed {to transmit impulses representing the thousands digit overthefundamental circuit to the distant mechanical 'oflice (Fig, 8) toset'the incoming selector (IS) thereat'. This operation will behereinafter more fullydescribed-f The key 605corr'espond'ng to thed1git5 is now depressed in accordance with thetens digit of the desirednumber closing a. circuit to operate relay1031 as follows groundatarmature 647' of relay 619, 654, resistance 650, right contact of key605, 680, 627, 503, brush. 541, 5012, brush 563,927, brush 964, thirdterminal of are 954, left windings of battery. Relay 1031 which issensitive operates'hut relay 1032 which is marginal does not operate dueto the high resistance of resistance 650 in series with it. Relay- 1031operated, locks'through its right winding by wayof lead 1000 tobattery,With the'key 619, 654, 674. left contact of key 601, 644, 629, 505.brush 543. 5014, 5001, brush 562, 926Qwindina' of relay 916, 948,brushf963,

605 depressed, a circuit is"alsoclosed fto'opr crate relay 916'as.follows: ground at armature 647 of relay619, 654,resistance 651, leftcontact of key 605," 644, 629, 505, brush .543,

5014, 5001, brush 562, 9 26, winding jofp relay 916,-. 948, brush 963,third terminal of are 953, right winding ofjrelay 1030, .1000, tohattery.i- Relay 1030 which is marginal does not operate due' tothe:jhighifresistance "of the coil .651 inserieswith it. Relay916operated operates relay i917 and, stepping magnet 956 which functionsfinthe manner .relays1031 and 1032in series, 1000, 914, to

previously described, and when relay 916 releases by the release of key605 and relay 917 by the complete operation of stepping magnet 956, thecircuit through the stepplng magnet is opened and it releases advancingI its brushes 960 to 965, inclusive, to the fourth terminal of each ofthe arcs 950 to 955, respectively...

We are now ready to. send the units digit which in this case is thedigit zero and accordingly numerical key 600, corresponding to the digitzero, is depressed.

The key 600 depressed operates relay 1041 as follows: ground, armature647 of relay 619, 654, resistance 650, right contact of key 600, 680,627, 503', brush 541, 5012, brush 563, 927, brush 964, fourth terminalof are 954, left winding of relays 1041 and 1042 in series, 1016, 986,to battery. Relay 1041 which is sensitive operates but relay 1042 whichis marginal does not operate due to the high resistance of resistance650 in series withit. Acircuit is also closed to operate relay 922 asfollows: from ground at armature 647 of relay 619, 654, resistance 651,

left contact of key 600, 645, 628, 504, brush 542, 5013, 5003,brush564,928, winding of relay 922, 948, brush 963, fourth terminal of 953,right winding of relay 1040, 1000, 914 to battery. Relay-922 operatesbut relay 1040 which is marginal does not operate due to the highresistance of the resistance coil 651 in series with it. Relay 922operated operates relay 917 and stepping magnet 956 in the mannerpreviously described.

When key 600 is released, relay 922 releases. When the stepping magnet956 is fully operated,-relay 917 releases and the holding circuit forthe stepping magnet 956 is openedallowing the stepping magnet to releaseandadvance the brushes 960 to 965, inclusive, onev step in ananti-clockwise direction to the fifth terminal of each of the arcs 950to 955, respectively.

Sending impulses.

- An important feature of this invention is that after two digits (thethousands and hundreds) have been registered, the sender will proceed totransmit the first digit and for each additional digit recorded, thesender will proceed to transmit impulses corresponding to the nextsucceeding digit over the fundamental circuit to the distant mechanicaloflice (Fig. 8). One digit, however,

4 is always held-in reserve by the sender until all the digits have beenregistered by the operator.

When the operator inserts the plug of the cord 10 in the jack 807 in themanner hereinafter described, certain changes occur in the senderindicating that all the digits transmitted have been recorded whereuponthe sender proceeds to transmit the digit which has been held in reserveup to that time. This will be hereinafter more fully described.

After the second digit (hundreds digit) was recorded, the brush 960 ofthe recording switch was advanced to the third terminal of the arc 950closing an obvious circuit to operate relay 900 through its rightwinding to ground at the brush 960. Relay 900 operated looks through itsleft winding by way of lead 987, strap terminals of the arc 952 of therecording switch, brush 962 to ground. Under certain conditions, by wayof lead 988 and the strap terminal of are 975 of the sending switch toground at brush 985 in a manner hereinafter more fully described.

Thousands selection.

We are now ready to transmit impulses over the fundamental circuit tothe distant office to set the selector. switches thereat providing thefundamental circuit is closed and, accordingly, we must now test thefundamental circuit before allowing any impulses to be transmittedthereover. A circuit is closed to operate relays 929 and 811 as follows:battery, right Winding of relay 811 (Fig. 8) trunk conductor 823, 432,422, 498, 498, brush 561, 921, 989, winding of relay 929, 920, brush560, 5015, 497, brush 433, trunk conductor 822, left winding of relay811 to ground. Relays 929 and 811 operate after the circuit is properlyclosed. The function of relay 811 will be hereinafter more fully,described.

telay 929 tests the incoming selector (18) (Fig. 8) as soon as the trunkcircuit and an idle sender circuit are found. Relay 900 operates afterthe second (hundreds) digit of the number of the called line has. beenrecorded in the sender and the brushes of the recordingswitch haveadvanced to the relay 900 may lock third terminal of each ofthe arcs 950to ing circuit of the stepping magnet 976 is opened and the brushes 980to 985 inclusive, accordingly remain atrest upon the second terminal oftheir respective arcs. A circuit is now closed to operate relay 946under control of the interrupter 937 as follows: battery at the armatureof relay 913, 986, 993, the second terminal or arc'971,

984 resting upon the

